Accurate health-related quality of life (HRQOL) measurement is a critical aspect of assessing health, and the success of health care interventions. However, psychological research indicates that memory-based methods, typical of HRQOL assessment, are often biased by extraneous factors, like mood state at the time of assessment and by information that comes easily to mind. The purpose of this application is to evaluate existing recall-based approaches to HRQOL measurement against two new tools for measuring HRQOL that have been designed to be robust to memory biases. Specifically, we propose to examine Ecological Momentary Assessment (EMA), which utilize real time measures and therefore are not subject to memory biases, and a new diary-based approach to measuring quality of life, the Day Reconstruction Method (DRM). The DRM is designed to be similar to EMA in terms of being robust to memory biases, but is much less burdensome and expensive. We intend to begin to test the usefulness and validity of these measures among lower extremity osteoarthritis patients (LE-OA) and in a comparison group of healthy older adults. Our aims are to 1) determine the feasibility of administering EMA and DRM measures in an older OA population, 2) evaluate the validity of EMA and DRM for use as HRQOL measures, and 3) determine whether a DRM-based HRQOL measure reduces memory bias. To achieve these aims, we propose a longitudinal observational study of two groups of older adults, a group with LE-OA and a healthy comparison group. All participants will wear Actiwatches, which are wrist watch accelerometers that can also prompt participants to respond to a short questionnaire several times throughout the day. They will wear these for one week, at the end of which we will we will administer traditional recall-based measures that ask about symptoms and function for this same period of time. We will repeat this procedure twelve months later. These new methods could prove to be extremely valuable for health care researchers. The DRM is a cutting edge methodology that is much less costly and burdensome than EMA methods but to our knowledge, it has not been tested as a method for measuring HRQOL measure in patients.